Gliding arc gas discharge

Abstract

The sliding arc discharge starts at the shortest distance between the electrodes, then moves with the gas flow at a velocity of about 10 m/s and the length l of the arc column increases together with the voltage. When the length of the gliding arc exceeds its critical value lcrit, heat losses from the plasma column begin to exceed the energy supplied by the source, and it is not possible to sustain the plasma in a state of thermodynamic equilibrium. As a result, a fast transition into a non-equilibrium phase occurs. The discharge plasma cools rapidly to a gas temperature of about T0 = 1000 K and the plasma conductivity is maintained by a high value of the electron temperature Te = 1 eV (about 11 000 K). After this fast transition, the gliding arc continues its evolution, but under non-equilibrium conditions (Te ≫ T0). The specific heat losses Wcrit in this regime are much smaller than in the equilibrium regime (numerically about three times less). The discharge length increases up to a new critical value of l ≅ 3lcrit. The main part of the gliding arc power (up to 75-80%) can be dissipated in the non-equilibrium zone. After the decay of the non-equilibrium discharge, the evolution repeats from the initial break-down. This permits the stimulation of chemical reactions in regimes quite different from conventional combustion and environmental situations. It provides an alternative approach to addressing energy conservation and environmental control. In the first part of this paper, the gas discharge physics are described. The second part reviews the chemical reaction in the gliding arc plasma and some possible applications. © 1999 Elsevier Science Ltd. All rights reserved.